Abstract: Fuel oil containing sodium salt, potassium salt and solid matters is purified by separating the fuel oil into fuel oil and sludges by a centrifugal separating means, thereby removing the sludges from the fuel oil, and mixing the fuel oil freed from the sludges with water, and separating the resulting liquid mixture into fuel oil and water. Removal of the salts and the solid matters from the fuel oil can be attained at the same time very effectively with a reduced frequency of cleaning a filter or by omitting the use of the filter, with or without using an emulsion breaker.

Abstract: In a liquid-liquid centrifugal extractor wherein a liquid of greater specific gravity is introduced into an inner peripheral portion inside a rotor, while a liquid of smaller specific gravity is introduced into an outer peripheral portion, and the two liquids are brought into direct contact by exploiting the difference of the specific gravities thereof, to move an extract contained in one of the liquids into the other liquid, pipe means or groove-shaped members having a large number of small holes and serving to distribute the liquids are arranged in the outer peripheral portion and the inner peripheral portion inside the rotor in such a manner that they extend in parallel with a shaft for the rotor and that the holes of the means or members in the outer and inner peripheral portions face each other.